Each flight log entry usually
represents a launch or test day, and describes the
events that took place.
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We had another good launch day with
NSWRA. The weather was a little foggy early
on, but then it turned out to be an almost
ideal day for rockets with mild conditions,
no clouds and very little breeze. We got to
launch our upgraded Polaron rocket and set a
personal best altitude in the process.
Before we get into the day's events here is
a little info about two new rockets flown on
the day.

Polaron VI

About a week before the launch day while
inspecting the Polaron V main stage I
noticed that some of the bottles were
showing quite severe stress marks around the
bottle necks. We decided to play it safe and
replace the bottles. We had a number of the
2L spliced pairs (3.6L capacity) ready to
go, and with having the 22mm Tornado
couplings on hand we decided to screw
together 3 of the spliced pairs. We kept the
lowest 2L bottle from the Polaron V rocket
as it had all the booster retention tubes, fins and guide rail
lug already attached. This was also
convenient since the bottle also had a
Robinson coupling which we wanted to use for
Jet Foaming.

During the week we pressure tested the
three sections to 130psi - the launch
pressure. One section sprung a very
small leak, but we decided to change it for
a new one as
we imagined the "tiny crack in the dam"
scenario. In the process we managed to
increase the volume of the rocket by almost
3 liters while only gaining an extra 15
grams! With the exception of the one
Robinson coupling both the main stage and
boosters were all spliced and Tornado
coupled together.

Axion

Axion is a new rocket based on the 90mm
body diameter size. The rocket is entirely
made up of spliced pairs joined with the
22mm Tornado couplings. We will eventually
use this rocket to do experiments with
larger nozzles and long launch tubes. The
removable fin section was taken from the
Hyperon
rocket, as was the nosecone and deployment
mechanism. When it was assembled, we
realised that the little white parachutes we
have been using are just too small for a
rocket of this size. We made a quick
parachute out of the lightweight rip-stop
nylon we bought a few months ago. One of the
nice things about the material is that it
packs very small and we were able to fit the
bigger parachute in the same space as the
smaller one.

We have found that the spliced pairs and
couplings can make pretty straight rockets
without much effort. If you construct
rockets this way an easy way to check your
alignment is to look down the nozzle and you
can easily see if the other joins are
aligned or not. All the couplings should look
concentric. The couplings also allow us to
unscrew the rocket half way along which
makes transportation and storage much
easier.

Launch Day Events

We arrived at the launch site just
before 8am and found that there was
quite a heavy fog at the launch area. We
figured we'd set up slowly and wait
until it burned off. But soon we
realised that this was a unique
opportunity to launch a rocket with a
video camera to see if we could get
above the fog. So we quickened the pace
to get the launch in.

As we assembled our old medium
launcher and were blowing water out of
the hose (because I forgot to purge it
after the last pressure test) I noticed
that the brass riser tube under the
release head was blowing bubbles out the
side. There was a hairline crack in the
tube. I guess after 1.5 years or so in
service and perhaps a couple of hundred
launches under its belt, it must have
just work hardened and finally cracked
under the repeated pressurisation
cycles. We will replace it with a
stronger copper pipe to stop that from
happening again.

We thought we might miss the fog
launch opportunity as the only other
launcher we had was the Polaron
launcher, but the problem was the it
uses a different guide rail system. So
we quickly decided to adapt the guide
rails from the medium launcher to the
Polaron launcher and secured them with a
few wood screws and some wire. We had to
use the guide rail extensions because
Axion stands at almost 2 meters tall.

We weighed up the launch pressure as
we wanted to go high enough to get above
the fog, but not too high since there
was a serious danger of it drifting out
of sight in the fog. Settling on 125psi
which we guessed would give the rocket
about 400 feet, we launched it and it
promptly disappeared in the fog. A short
time later we heard the parachute pop
sound so we knew it was under parachute,
but could not see the rocket. We were
looking in all directions until it was
spotted descending perhaps 30 meters
away. We quickly downloaded the video
and altimeter data to see if the rocket
made it. The video clearly showed the
rocket was flying above the fog. It was
a fun experiment to do, but if we ever
get the opportunity to do it again then
we will need to have a siren on it to
help us locate it.

Pretty soon after that the fog had
lifted and we converted the Polaron
launcher back to the ... well Polaron
launcher. It took us about 30 minutes to
set up the Polaron VI rocket on the pad
and fill it, secure the boosters, and
all the parachutes.

The launch and flight were pretty
close to ideal. The boosters separated
right on cue and simultaneously and the
rocket just continued to power up and
up. With the higher capacity we had
2.4Liters of water and foam mix in it
and trying to get it all out through a
7mm nozzle takes a while. The foam trail
extended all the way to apogee. The only
couple of minor issues were that the
rocket had a bit of a spin, which didn't
really affect the flight but made for a
more dizzy video. The other issue was
that the parachute deployed a tad too
early while the rocket was still
ascending, and pointing vertically,
although judging by the onboard video,
the rocket would not have gone much
higher.

The downloaded altimeter data showed an
ideal curve with a peak at 637 feet!
(194m). This was our new personal
best and directly measured altitude.
This was 20 feet higher than the
Acceleron +
Tachyon 2 stage rocket. It was also
over 125 feet higher that with the
smaller Polaron IV rocket. Both the
Acceleron and Polaron rockets still have
plenty of room for improvement so it
will be interesting which combination
ends up being better.

The last flight of the
day for us was the Polaron VI rocket
again with the same setup as the
previous launch. This time the rocket
took off vertically, but just before
booster separation the rocket started
pitching over and continued to do so. We
reviewed the video frame by frame to see
if we could spot what had happened but
there was nothing obvious as a stuck
booster. the rocket looked like it was
pitching over even before separation.
Our only plausible explanation at this
stage is that the rocket was marginally
stable. With so much water in the tail
section of the rocket it may have had
the Cg too far back for too long.

In any case the rocket now being pointed
towards the ground kept accelerating
until impact. The parachute deployment
delay was just set for too long.

On a good note, all the electronics
survived well, however, the camera did
not record the flight. On impact there
may have been an interrupted power
supply so the data would not had been
finalised and therefore the file was not
accessible. The altimeter data was
recovered although it did record a -7000
foot drop sample on impact.

All the 2L spliced pairs were damaged
beyond repair, and the nosecone needs to
be rebuilt, but otherwise the entire fin
tail section with all the tubes and
nozzle survived well and will be reused.
We can also reuse all the tornado
couplings. So ultimately the
repair bill will be the PL glue used to
glue the new recycled 2L bottles
together.

The other important
lessons learned from this day were:
- The new spliced pairs, both 1.25L and
2L are working well with the Tornado
couplings.
- The parachute deployment mechanisms on
the boosters also worked well.
- The thin walled brass booster retainer
tubes were up to the job.
- The rubber band attachment points at
the top of the boosters worked well.
- Axion's new simple parachute worked as
designed.

Good launch but
rocket started pitching over
significantly after booster
separation. Booster sep appeared
simultaneous. Rocket accelerated
towards the ground, but hit before
parachute could deploy. The rocket
was destroyed on impact. No video
recorded, altimeter data available
but a little erratic. All
electronics and tail section
survived.